Charge pressure deviation, N75 thoughts

Okay... one or two comments that might or might not deserve their own thread.

after mjbach was talking about here problem, it started me thinking a bit more...

When I experienced no boost this weekend i got the Charge Pressure Deviation 17958 code. I managed to limp to a service stop on the turnpike and swap the EGR and the Boost controllers (identical on A4 cars). Now I know the N75 (boost controller) was not working properly to make boost and putting it on the EGR isn't such a bad thing right?

Now I haven't verified it yet, but looking at the duty cycle it seems that the ECU is happy with what the EGR controller is doing. But i'm wondering if it is indeed doing anything (yeah I know - hook up the vacuum gauge to see... I will). But if in fact you have a dead (known) N75 and a working EGR controller, adn you swap them you'd effectively get an Epsilonian type device for free. The feedback on the controller is correct, but it isn't pulling a vacuum and therefore not activating the EGR valve...

BUT before everyone starts buying up dead N75 controllers from scrap yards or from people who've had them die it needs to be tested (i'll see about testing it this weekend or sooner)... but its a thought.

Geoff you have a bad MAF. The MAF should detect the opening anc closing of the EGR...Keep in mind a MAF that is functioning properly will easily be able to detect the opening and closing of each intake valve.

If you are not triggering a code this points directly at a bad or reduced sensitivy MAF sensor.

DB

Maf is working fine too . . . its reading what it wants to read . . .

An interesting thing to add to the observations. The Boost was gone again!

I had VWTool running when it happened and whadda ya know - N75 % value was pegged at 92% and I wasn't getting any boost.

Sooo I managed to limp home (5 miles no big deal) leave the car running and check the vacuum in the line to the turbo... turns out there was none (i've still got the 'T' into the VNT vac line and can hook a vac gauge up easily). Sooo I try the "output tests" with the vacuum gauge hooked up. Well whadda ya know it worked again. The EGR seemed to be working too it was buzzing and buzzing but then engine wasn't really sounding as different as I would expect it to if the EGR was opening all the way up.

It has me wondering now,,, I've checked the movement of the VNT mechanism and it seems fine. I suppose both the controllers could be old and toasted now . . .

I'm pretty sure the VNT duty cycle is inverted. In other words, 92% means 'no boost', and 0% means full boost. So, the ecu was ordering no boost when you were expecting full boost?

Braindead,
Look at this: Map-log green:expected MAP, yellow: actual MAP
Passat, 81Kw VNT: upgoing duty cycle: upgoing boost.
The pressure deviation is caused, in my opion, by the duty cycle and that valve (N75) again is controlled by the ECU.
Therefor: why is the ECU causing those fluctuations?
GeWilli: Is it possible to dampen those fluctuations, preventing the ECU going into limp mode?

If you go to basic settings channel 11, it will test your turbo by cycling it to the full on and full off position. Can you check this on your car for me? Mine reads 99.9% when it is in the off cycle. This could make sense because at idle the duty cycle is at about 25%, meaning the turbo is just waiting for more fuelling and more engine rpm to spool up. It would increase the responsiveness if it is 'on' at idle. The computer could also be reacting rate of change of charge pressure. The faster the pressure rises, the more the computer shuts off(higher %) the turbo. This would also follow the charge pressure graph. Do you have a graph with a pixel shift of 15? You might notice that the duty cycle lags behind the requested MAP and actual MAP. In a full throttle condition at 3500 rpm, do you really want the vanes of the turbo in the on position? Your turbo would explode. I could be totally wrong, though.

Take a look at the right side of your graph. You have 0% throttle and your engine is winding down from 3700rpm yet your duty cycle is 60%. How could it be giving zero boost if 60% was more on than 0%? It couldn't. Why do you have the same boost pressure at 3000rpm and 60%, as idle and 24%?Higher duty cycle means less exhaust power to the turbine.

At the left part of the graph the throttle is shut, duty cycle is approx. 24 % and low on boost power. That makes sense to me. I did not notice the strange thing on the right part of the graph! You are right! It looks very odd. As if the N75 is not controlling the turbo?! I can't think of a reason why. Any suggestions?
The graph as you requested: Log with PS=15

The turbo is powered by exhaust gases. The vanes channel the gases toward or away from the turbine that drives the compressor. At idle, there is not very much exhaust gas to drive the turbine, so regardless of how 'on' the vanes are pointing, you are going to see very little boost. So you might as well leave the turbo in the 'on' position. Once you hit the pedal, you get more exhaust gas and hotter exhaust gas coming out of the engine. Since the turbo is already on, there is no time wasted to turn it on. All the ecu has to do now is to reel in on the amount of exhaust going to the turbine according to engine rpm and fuelling. Higher rpm and fuel, LESS gases directed at the turbine(higher %). Lower rpm and fuel, MORE gases directed at the turbine. Remember, the VNT turbo is designed to be extremely responsive to prevent particulate matter out of the pipe. Got it?

I should also mention that the ECU most likely doesn't drive the N75 by itself. It will have a buffer circuit driving the N75. Most likely a power transistor, and it just happens from a cheaper is better sense, the cheapest method involves inverting the signal the ECU sends. That's why the VAG-COM duty cycle looks inverted.

By the way, assuming a time/division scale of 2s/div., it takes less than a second for max actual to cross the max requested boost line on your chart. Your linkage is clean and working fine. Also, actual peaks at about 19.5 psi, pretty good considering you've got a stock 110.

Geoff or Pete, could you pull about 15" of Vac on the Vac side of an N75 as a test. While trying to clear up some recent doggieness, I vac tested the turbo actuator- no leakage, EGR actuator at Vac line- no leakage, but when applying Vac to the Vac side of the N75 there is rather rapid leak-down, even if I block of the other 2 nipples of the N75. Opinions?
Oh, bye the way, MAF is new and well within spec.

you mean MAF or MAP within specs?

I'll check mine for you sometime this weekend.

I've ordered the N18 and N75, since the N18 is failing as a backup N75 . . . I'm gonna swap the N75 back in place to see if it works any better (breaks less than the N18).

Paul, do you have a boost guage installed? I'm starting to think that maybe people are experiencing a dead N75 and replacing a MAF . . . with out a boost gauge you might not be able to tell...

And since my N75 is the old school style (1H0 instead of 1J0) i've ordered the plugs to convert it over. Will update on that bit of cost savings...

I'd wager that these are Time dependant failures. Probably life span is 3-5 summer/winter cycles... but thats just a guess...

Geoff or Pete, could you pull about 15" of Vac on the Vac side of an N75 as a test. While trying to clear up some recent doggieness, I vac tested the turbo actuator- no leakage, EGR actuator at Vac line- no leakage, but when applying Vac to the Vac side of the N75 there is rather rapid leak-down, even if I block of the other 2 nipples of the N75. Opinions?

Oh, bye the way, MAF is new and well within spec.

Click to expand...

I just tried the leak down tests on a virgin N75. Same leak down results.

Thank-You gentleman, I'll continue the search. I did not check the non running output of the MAP, or for that matter the under acceleration output, I'll report back. Oh yeah, almost forgot to ask, what is the full application Vac reading for the turbo actuator? Thank-you again.

a little update.

This past week I was able to get the proper controllers in place. The New N18 and N75 are installed (using the new style connectors and the newer/cheaper controllers) and HUGE difference.

These two jobbers are NOT the same - similar and maybe useful as a test BUT not the same.

Big thing is boost response - much quicker and more precise control with the white top controller. BUT I'm seeing 3-5PSI higher spikes (yeah . . . 28-30 with this controller and no dawes).

No i still haven't hooked the modified Dawes device back up. Boost is crazy now. Like it was before. The EGR is just too slow and not sensitive enough to run the VNT... But now that I'm back to normal its all better.

sort of . . . boost is still way out of control

GeWilli, could you show us some graphs here?
'One drawing says more than a thousant words'. (or something like that)

sorry - i'm not sure I have any graphs of the MAP readings with the N18 in place.

and I'm not changing the connector back to test it . . . BUT

I think i might just dissasemble my N18 and N75 to see what the guts look like . . . and I will have pictures of that

Willi, source and cost for N75 please, also for anyone interested, key on, non running readings for MAP sensor were 877, atmospheric sensor 991. Is this disparity anything to be concerned about? Thanks!

that difference is what I see. Not so much MAP problems as baro calibration? Dunno but I see that difference too as do a few others ...

costs:
I ordered from Impex this time . . .
[ITEMS PURCHASED]

N18Part number: 1J0906627 CONVERTER
Price: $39.76 Quantity: 1 Total: $39.76
N75Part number: 1J0906627A CONVERTER
Price: $58.35 Quantity: 1 Total: $58.35

These two pars are what are needed to adapt from 1H0906627(A) to 1J0906627(A).

Part number: 1J0973722 HOUSING
Price: $5.23 Quantity: 2 Total: $10.46
Part number: 1J0971921K CAP
Price: $2.95 Quantity: 1 Total: $2.95

Simpley remove the cap from the N75 plug and the wires from each of the old Housing and replace the wires and put the new cap on the N75 plug and you are done

Check prices for 1H0906627A and you'll realize why i've gone the route to change plugs.

I managed to limp to a service stop on the turnpike and swap the EGR and the Boost controllers (identical on A4 cars)

Click to expand...

NOT IDENTICAL (for the record)

and then there is this issue added from a different thread:

originally posted by Boundy
What really bothers me, and scares me, is that GeWilli can hold a high sustained boost by fiddling with the pedal. That means the VNT vanes aren't opening up enough to reduce the driving force on the turbine. Or his VNT is getting stuck. Or the VNT rod was shortened back when that was en vogue.

Click to expand...

Boundy - no i never did it when it was 'En Vouge' - almost did - but refrained from it...

But you might be on to something - regarding the VNT getting stuck...

with the new freaking N75 I had no boost leaving a toll booth again (I'm getting a phobia of leaving toll booths now) - running an output test fixed it... and running the output test is like moving the VNT by hand - full vacuum to no vacuum and then full vacuum ....

I might try and get on a lift before too long so i can really get back there and under there and see what is going on . . .

But the new N75s did squat gotta be the chip and the injectors - and all that GD smoke I'm making . . . (yeah smoking even with B20)

Yeah new N75s didn't do much at all to help GRRRR but on the ohter hand i've taken the old ones apart and they look pretty cool (pics to come soon). And it narrows down the potential problem... (good and bad I guess) . . .

so here i am guilty of throwing $138 of parts at a car . . . which if you really look at it all . . . and the cost savings I've had doing all my own maintenace - its pretty insignificant . . . AND I just have to keep telling myself that if I hadn't been soaking up info here - and hadn't met the other like minded folks that work to understand this beast of a machine - and had been relying on the dealer to make it work . . . It would never get fixed and I'd probably be out over $200 without any resolution to the problem and would be much farther away from the solution than I am now!

Thank you all for this forum - this place ROCKS!
/positive spin

Hmm... sticking turbo linkage? I never thought of that.

Okay - just to add to the range of info and to fill out the story:

1J0 and 1H0 controllers are identical. I swapped the connector back on mine and tested a known good 1H0 in place of the new style connector 1J0. Identical performance.

So that bit out of the way:

Boost problem. Still there. The issue it seems is that the COMPUTER is acutally what is preventing boost. (just found that out this morning).

I have a vacuum gauge (cheapo but for relative vac is works) and the car did its whole no boost thing again. Well the car didn't even try to pull a vacuum down on the VNT lines. Meaning the ECM is saying NO BOOST FOR YOU (in my best soup **** voice).

BUT this time with no boost request I was still able to MAKE almost the proper amount of boost well not quite but it came close to the 1100-1200 mbar that the car wanted (which is 200-300 over zero). Duty cycle was curious. ECU was saying 92.4% as in that was the limp mode spec.

I checked basic settings - and whadda ya know - (at idle coasting down from 70 mph) the vacuum gauge went to full vacuum and back to zero vacuum just as the computer was asking for. But then when i resumed fueling and put the clutch back in under normal settings . . . still no boost and still 92.4%

Output tests fixed it - (not sure if it is the fuel cut off soloniod shutting the car down and resetting it or if its the cycling of the N75 that is fixing it).

---

Current Hypothesis: Excessive smoke from having Ups chip + Sprint 520s (0.205s) injectors (not a reccomended combination now it seems not even by Ups folks from reading - too many issues) and excessive boost and with the Dawes installed all lead to lots of smoke - infrequent full request runs - and slow build up of soot reducing the travel of the VNT vanes and effecitvely reducing the range of travel on the wrong side of the throttle and basically (seemingly) sending the car into limp modes. 3 toll booths - 2 cruise control resumes and once going up hill and making an accelleration pass (I-70 in PA south of Breezewood).

So, the guess seems to be Turbo mechanism, specifically the VGV mechanism, Thomas has a nice web page with just the problem. Although I think my problem is that the linkage is a whole lot worse than his.
http://www.technologie-entwicklung.de/Gasturbines/VNT15-Turbo/vnt15-turbo.html
thats the link - and thats what i'm gonna atempt this weekend. And hopefully I can just put my turbo back on.

Sooo - if you are making smoke - be prepared to clean up the turbo at some point I guess... I'll update as it progresses.

BTW the code I got from yesterday morning's problem was 00575

and the factory manual says verify N75's condition and response (and I have and it's perfectly good)

if N75 checks out okay

"renew turbocharger"

This forum member's about to see if they really mean it or if they are just too lazy to dissasmble and clean it . . .

Your turbo is going to be toast if you continue to peak at 30 psi, the shaft will snap shortly. Didn't you just change chips? You are hitting limp mode because you are exceeding specified boost by .2 bars, it's an internal ECU protection but only acts as a warning, cycling the ignition key resets the system. once is bad, keep doing it and your turbo will eventually grenade. Now wouldn't that be ironic for the chicken little of turbo failures to blow his up? You could intall the dawes device to regulate your boost better , but that would be a bandaid, using your words.

valois said:
Your turbo is going to be toast if you continue to peak at 30 psi, the shaft will snap shortly. Didn't you just change chips? You are hitting limp mode because you are exceeding specified boost by .2 bars, it's an internal ECU protection but only acts as a warning, cycling the ignition key resets the system. once is bad, keep doing it and your turbo will eventually grenade. Now wouldn't that be ironic for the chicken little of turbo failures to blow his up? You could intall the dawes device to regulate your boost better , but that would be a bandaid, using your words.

Click to expand...

I realize that yes - it will be toast if I continue to peak - fact is I'm not. Fact is the only think keeping me from hitting 30 PSI before was the dawes.

I just changed chips and it helped with boost control quite a bit, but it also was in the middle of a spiral downturn of the problem with the turbo.

For the record - with the Rocket chips i was not spiking at 30 PSI, well I wasn't until the vanes packed the soot up even more. But the chip did not stop this problem (the theorized soot build up in the turbo vanes).

Sure would be ironic, if I blew my turbo, but it also would be another nail for a combination that somepeople say is perfectly safe.

Well thats why I have a boost gauge, and watch the gauge when accelerating.
The added vacuum gauge allows me to verify what the N75 is trying to do, and having spend lots of time examining the VNT movement under vacuum control of a Mity-vac and the engine's basic settings and output tests i know that the vacuum gauge on the dash is telling me exactly what the car is doing with the vane . . .

very cool I think. but I wish it was under better circumstances than a measure to make sure my car can last until I can have it out of comission for a day or two.

valois said:Now wouldn't that be ironic for the chicken little of turbo failures to blow his up? You could intall the dawes device to regulate your boost better , but that would be a bandaid, using your words.

Click to expand...

Speaking of Chicken little... (Famous Rene lines of the day) Your turbo is gonna blow because of restriction...

Rene here is that saddest part about you even posting in this thread, Geoff is NOT peddling gimmick filters or is he posting false information to support his sales.

Geoff has presented the facts surrounding his problem and others have been suggesting ways he could get it fixed or addressed, again in true TDIclub form people helping people that is until you wash up on the beach stinking up the place once again.

Lets not forget that Geoff has been running an Upsolute chip also associated with quite a few blown compressor wheels, most of which go un reported because of fear you are going to chime in and flame them.

The difference here is that Geoff myself and other will not stop posting due to your belligerent remarks and defamation nor will stop supporting the TDI community here because you go out of your way the threaten and intimidate. Why Fred has not banned you permanently is beyond me but after all it is his forum so his rules prevail.

The saddest part about your miserable existence is that when people disagree with you its like clockwork, out come the personal attacks and name calling. Again go back to that bridge you hide under or just simply go away, you're not welcome around here and that truly is the prevailing opinion of the masses.

DB

I'm going to have to remind the membership of the forum rules. In particular:

[3]No flaming of other members to incite or perpetuate a conflict or argument. ANY personal attacks or name calling will get you banned.

Click to expand...

Any chance your prolem with the turbo is the cat, converter like what happened with DBWs maybe with your high miles it is clogged up.

Drivbiwire said:

valois said:Now wouldn't that be ironic for the chicken little of turbo failures to blow his up? You could intall the dawes device to regulate your boost better , but that would be a bandaid, using your words.

Click to expand...

Speaking of Chicken little... (Famous Rene lines of the day) Your turbo is gonna blow because of restriction...

Rene here is that saddest part about you even posting in this thread, Geoff is NOT peddling gimmick filters or is he posting false information to support his sales.

Geoff has presented the facts surrounding his problem and others have been suggesting ways he could get it fixed or addressed, again in true TDIclub form people helping people that is until you wash up on the beach stinking up the place once again.

Lets not forget that Geoff has been running an Upsolute chip also associated with quite a few blown compressor wheels, most of which go un reported because of fear you are going to chime in and flame them.

The difference here is that Geoff myself and other will not stop posting due to your belligerent remarks and defamation nor will stop supporting the TDI community here because you go out of your way the threaten and intimidate. Why Fred has not banned you permanently is beyond me but after all it is his forum so his rules prevail.

The saddest part about your miserable existence is that when people disagree with you its like clockwork, out come the personal attacks and name calling. Again go back to that bridge you hide under or just simply go away, you're not welcome around here and that truly is the prevailing opinion of the masses.

DB

Click to expand...

Pete like i said give it a rest, I must of missed where you were elected to represent the rest of the forum. The only reason why I stopped posting was because of you. The moderators refused to reign you in, even now you have attacked me in several threads unprovoked. What do we see? A very weak response from MOGolf. I have not even mentioned air filters Pete, You are too full of yourself.
Gewillie,
Were you triggering limp mode before? I doubt your vanes are stuck, I thought they passed the vag com test? if so they are operating, do a boost log specified to actual. Find out where you are straying from specified boost, should give you an idea of what is wrong.

Cat could be clogged up but . . . that doesn't seem consistent with the symptoms of over boost -

The VNT mechanism is not smooth Rene, and the Duty cycle on the VNT both read by the vacuum and the vag-com point towards the vanes not opening up enough, generating too much boost. The car does make quite a bit of smoke - should say did. Now with the over boost - no smoke - none, due to overboost. I've got dozens of logs from late, and from some 60-90 runs all with bigger injectors and with both chipsets. I ran for a while with the N18 and even with that it still did it but the response was quite a bit different. I plan to document with images what I find, i will have another michigan forum member with me who has replaced his turbo after a catastrophic failure, adn then again after he found a cracked oil line.

My theory now is that the 4000 miles i drove over 3 weekends somewhat babying it to see what kind of mileage I could get (55 mpg) combined with the fueling profile combination of the chip and injectors - and the 15,000 miles running with bigger injectors and a 3.8 IQ with the chip. I would guess that the soot has packed up in the turbo and reduced the vanes. Not an unheard of problem. I'm skeptical about the cat- clogging based on TDImeister's problems, but maybe the effects of back pressure on the VNT are different than the GT-15 or KKK on the B4s.

I'm tackling this problem with full personal responsibility, and some gracious, and knowledgeable help from fellow forum members. Am I ready to eat the cost of a new turbo? Yeah if that is what it takes. Am I happy about it? Nah. Am I happy I don't have to rely on the dealer to do this? Very much so.

Thank you all for the suggestions and the help.